Not the reason, do you have the final drive overall ratio?
Thats not what he said. anybody with a technical knowledge would know that.
That is correct. But the brick needs to be pushed through the air at a speed that suits you,you move the RPM range for a given speed in 5th suddenly you are in the limit area of the torque available for that being possible. Which is were we get to the requirment of the thorttle pedal at the slightest incline,. Yes the European motorways are better than the UKs but they are far from level. Slightest incline or headwind and you could find that holding 5th is not possible.
Bit techy I know but heyho

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J